This invention relates to a method for the manufacture of foam glass having high mechanical strength and a bulk density of less than 1 and to the foam glass manufactured by the said method.
Generally, foam glass has a low specific gravity, exhibits a heat insulating effect and enjoys a decorative value and, therefore, finds utility in interior and exterior decoration of buildings, for example.
Of the methods heretofore known for the manufacture of foam glass, typical are those to be described below. It has been known to obtain from glass by adding to glass a foaming agent such as carbon or calcium carbonate. This method attaches special emphasis to the decrease of bulk density. Consequently, it entails a disadvantage that the product shows a very low bending strength as of the order of 5 kg/cm.sup.2 and is heavily limited in utility. There is another disadvantage that because of its black color, the foam glass is not suitable for use in interior decoration which particularly attracts attention. Further, with this method it is difficult to manufacture foam glass of a small thickness. It has been customary, therefore, to obtain thin sheets of foam glass by first producing a thick plate of foam glass by the method under discussion and subsequently splitting the thick foam glass into several sheets having a desired small thickness. This naturally results in an increased cost of production.
A method whereby a foamed rigid product of calcium silicate-water glass system is manufactured has also been known. This product is not practical because of its inferior water-resistance.
There has also been known a method which utilizes for inclusion of bubbles in glass the phenomenon of gas generation during the decomposition of Glauber's salt. This method, however, has a possibility of causing environmental pollution.
In the circumstances, researches have been pursued after a process which is capable of manufacturing a novel foam glass using a glass-SHIRASU-water glass system. In this system, however, there is entailed a disadvantage that the range of composition in which the produced foam glass has a small bubble diameter and a small bulk density is quite limited.
An object of this invention is to provide a method for the manufacture of foam glass of the type having a small bulk density and excellent mechanical strength.
Another object of this invention is to provide a method for the manufacture of foam glass, which method is simple to carry out and does not entail formation of any noxious substance in the course of manufacture of foam glass.
Still another object of this invention is to provide a method for the manufacture of foam glass which is suitable for use as interior and exterior decorative materials for building.